1886.] on Thomas Young. 563 



eye, and the impinging against the retina, of particles inconceivably 

 minute. Huyghens, on the contrary, supposed the sensation of light 

 to be aroused by the impact of minute waves against the retina. 

 Young favoured the theory of undulation, and by his researches on 

 sound he was specially equipped for its thorough examination. Before 

 he formally attacked the subject, he gave, in a paj^er dealing with other 

 matters, his reasons for espousing the wave theory. The velocity of 

 light, for instance, in the same medium is constant. All refractions 

 are attended with partial reflection. The dispersion of light is no 

 more incompatible with this than with any other theory. Reflection 

 and refraction are equally explicable on both suppositions. Huyghens, 

 indeed, had proved this, and much more. Inflection may be better 

 explained by the wave theory than by its rival. The colours of thin 

 plates, which are perfectly unintelligible on the common hypothesis, 

 admit of complete explanation by the wave theory. In dealiuf^ with 

 the colours of thin films, of w-hich the soap-bubble offers a familiar 

 example. Young first proved his mastery over the undulatory theory. 

 In the pursuit of this great task, he was able to convert Newton's 

 Theory of Fits into the Theory of Waves, and to determine the 

 lengths of the undulations corresponding to the different colours of 

 the spectrum. 



We now approach a phase of Young's career which more specially 

 concerns us. The Royal Institution, as already stated, was founded 

 by Count Rumford, supported by many of the foremost men in 

 England. The King was its patron, the Earl of Winchilsea its 

 first president, while Lord Morton, Lord Egremont, and Sir 

 Joseph Banks were its vice-presidents. On the 13th of January, 

 1800, the Royal Seal was attached to the charter of the Royal 

 Institution. Dr. Thomas Garnet was appointed Professor of Natural 

 Philosophy and Chemistry. During his previous residence in 

 Bavaria, Rumford had ruled with beneficent but despotic sway, and 

 the habit of mind thus engendered, may have made itself felt in his 

 behaviour to Dr. Garnet. At all events, they did not get on well 

 together. On the 16th February, 1801, Davy was appointed 

 Assistant Lecturer in Chemistry, Director of the Chemical Labora- 

 tory, and Assistant Editor of the Journals of the Institution. 

 The post of Professor of Natural Philosophy was offered to Young, 

 and he accepted it. The salary was to be SOOl. a year. On 

 the 3rd of August, 1801, the following resolution was passed : — 

 " Resolved, that the Managers ajDprove of the measures taken by Count 

 Rumford, and that the appointment of Dr. Young be confirmed." 

 Young, it is said, was not successful as a lecturer in the Institution, 

 and this Dr. Peacock ascribes to his early education, which gave him 

 no opportunity of entering into the intellectual habits of other men. 

 More probably, the defect was due to a mental constitution, not 

 plastic, like that of Davy or Faraday, in regard to exposition. Young 

 now fairly fronted the undulatory theory of light. Before you is 



